The present invention relates to a circuit for and method of processing a television signal. More particularly, the present invention relates to a circuit for and method of processing an inputted television signal and outputting a video signal having an aspect ratio and image quality suitable for a connected television display, irrespective of the type of the inputted television signal such as a high definition television signal and a presently used standard television signal, and the type of the display such as a display with a wide aspect ratio and a display with a presently used standard aspect ratio.
An NTSC system is presently used as a standard color television system. In Japan and other foreign countries, as a new television system a High Definition TV (HDTV) is now being studied. In Japan, for exmaple, there is known a high vision system which is now being developed mainly by Nippon Hoso Kyokai NHK.
One of the characteristic features of the high vision system resides in that the number of scan lines is 1125 and the signal bandwidth is 20 MHz or wider which has information quantity about five times as large as the present NTSC system, realizing a very fine image (see NHK Technical Study Report, 1987, Vol. 39, No. 2, Serial No. 172, pp. 18 to 53).
Another of the characteristic features of the high vision system is that the aspect ratio of a screen is 9:16 having a horizontal side longer than the aspect ratio 3:4 of the NTSC system. Therefore, in order to display a high vision signal on a television display of the NTSC system, it is necessary to provide a signal converter called a down converter for adjusting the aspect ratio.
As the television system having such a wide aspect ratio (9:16), there is an Enhanced TV (EDTV) system of second generation also being studied in Japan (hereinafter abbreviated as EDTV-II).
The EDTV-II system intends to obtain a wide and fine image while ensuring compatibility with the presently used NTSC system.
The high vision system and EDTV-II system having a wide aspect ratio are expected to come into practical use at substantially the same time in near future, while continuing to use the presently used NTSC system. Therefore, if broadcast signals of various systems are all to be received, several television receivers are required to be newly bought and installed, which is not practical from the viewpoint of expenses and spaces.
It is an object of the present invention to provide a television signal processing circuit and method capable of receiving television signals of different systems with a single television receiver by discriminating the inputting television signals and selecting a proper signal processing circuit, irrespective of the type of an inputted television signal such as a high definition television signal (e.g., of the high vision system), an EDTV signal (e.g., of the EDTV-II system), and a presently used standard television signal (e.g., of the NTSC system).
More particularly, according to a first aspect of this invention, there is provided a television signal processing circuit and method capable of receiving a broadcast signal for any aspect ratio of a television display, for example, an aspect ratio of 3:4 and a wide aspect ratio (e.g., 9:16).
According to a second aspect of this invention, there is provided a television signal processing circuit and method capable of receiving a broadcast signal for any scan type irrespective of whether a television display is a single scan type display dealing with only one scan type or a multi-scan type display dealing with a plurality of scan types.
According to a third aspect of this invention, there is provided a television signal processing circuit and method capable of separately outputting a luminance signal and color signals irrespective of the type of an inputted television signal.